EP0333493A2 - Système de triangulation - Google Patents

Système de triangulation Download PDF

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Publication number
EP0333493A2
EP0333493A2 EP89302638A EP89302638A EP0333493A2 EP 0333493 A2 EP0333493 A2 EP 0333493A2 EP 89302638 A EP89302638 A EP 89302638A EP 89302638 A EP89302638 A EP 89302638A EP 0333493 A2 EP0333493 A2 EP 0333493A2
Authority
EP
European Patent Office
Prior art keywords
light
channels
detection channels
range
sweep
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP89302638A
Other languages
German (de)
English (en)
Other versions
EP0333493A3 (fr
Inventor
Carl Murray Penney
Nancy Hope Irwin
Nelson Raymond Corby, Jr.
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Lincoln Electric Co
Original Assignee
General Electric Co
Lincoln Electric Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by General Electric Co, Lincoln Electric Co filed Critical General Electric Co
Publication of EP0333493A2 publication Critical patent/EP0333493A2/fr
Publication of EP0333493A3 publication Critical patent/EP0333493A3/fr
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C9/00—Measuring inclination, e.g. by clinometers, by levels
    • G01C9/02—Details
    • G01C9/06—Electric or photoelectric indication or reading means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/46—Indirect determination of position data
    • G01S17/48—Active triangulation systems, i.e. using the transmission and reflection of electromagnetic waves other than radio waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/42—Simultaneous measurement of distance and other co-ordinates

Definitions

  • This invention relates to a time-based triangulation system.
  • a swept aperture flying spot optical ranging instru­ment has been developed and was offered as a product known as the MIG TRAKTM welding seam tracker. It is described in patent 4,645,917 - Penney, Roy and Thomas and patent 4,701,031 - Penney and Thomas. Although it provides the highest quality data among developed ranging systems, the maximum rate at which this type of system can acquire data is limited by the beam de­flecting acousto-optic cell to less than 100,000 range elements per second, and in fact runs at about 20,000 range measurements per second. To our knowledge no other developed system runs significantly faster. However, for applications such as a three-dimensional camera a much higher range data rate is needed; for example the present goal for printed circuit board inspection is 4,000,000 range elements per second. What is needed is a faster way to obtain range data while preserving the other high performance features of the MIG TRAK approach.
  • the speed of measuring range points in a swept aperture flying spot triangulation ranger system is increased by adding additional detector channels, each of which observes the surface at a different sensitive zone along the line which forms the intersection of the swept beam with the surface. Since all of the channels make use of the same swept beam, the beam source and deflector are used more efficiently, providing N range points per beam sweep, where N is the number of channels, rather than only one.
  • a flying spot triangulation ranger system is comprised of: means for providing a light beam and rapidly sweeping this beam across a surface in a given direction; multiple light detection channels optically coupled to separate detectors; and receiving lens means for focusing images of the light spot onto the entrance faces of the adjacent detection channels.
  • the respective detector As the light spot generated by the scanned beam crosses a small sensitive zone on the surface from which a detection channel can receive light, the respective detector generates an electrical signal pulse. These pulses are output at times that are a function of range to the surface; for every sweep of the light beam there are a plurality of range measurements equal to the number of detection channels.
  • the detection channels are preferably separate noncoherent fiber optic bundles, but may be solid glass, and typically there are ten to twenty such channels.
  • the entrance faces of the detection channels may be rectangular or square, and the sensitive zones "visible" to the channels have corresponding shapes.
  • the detectors may be photomultipliers.
  • Yet another aspect of the invention is a multiple channel flying spot triangulation ranger system comprised of a laser beam source and means for deflecting and sweeping the beam across the surface in the X direction; multiple fiber optic light detection channels each receiving light from a different sensitive zone along a scanned line; and a receiving lens.
  • Separate detectors sense the light delivered by the fiber optic channels and generate signal pulses, one per channel, at times respectively related to range to the surface. Means are provided for processing these signal pulses in parallel and calculating multiple range values.
  • the systems may include an aperture stop plate between the receiving lens and light detection channels having a rectangular slit to limit passage of light and increase depth of focus.
  • Mirror means such as polygons, may be provided to scan the light (e.g. laser) beam in the Y direction co-ordinated with the X direction sweep.
  • Processing means may calculate range values after each beam sweep, covering a strip of the surface, before moving a table supporting the surface by steps to scan adjacent strips.
  • a beam of light L is swept by beam deflector 10 along a line across the observed surface 11 over the time t0 to t1.
  • the intersection point of the beam with the surface a spot of light, passes through the region 12 viewed by the lens 13 and aperture 14; the latter is at the focal point of the receiving lens. Consequently, the scattered light from the point reaches the detector, photomultiplier 15, which puts out a sharp signal pulse at the time t z .
  • An electronic system analyzes this signal to derive a second signal encoding the time of the pulse.
  • the time at which the pulse is observed is a function of the range to the surface, and in fact varies nearly linearly with this range.
  • this system provides range information in the form of an encoded pulse time. If the surface is lowered by an amount ⁇ Z, then the position in time of the corresponding detected electrical signal pulse will shift to the left in time as is seen by comparing lines (b) and (c) in Fig. 2. By measuring the time shift ⁇ T the flying spot triangulation system can measure the change in range.
  • the light beam is swept across the surface very rapidly at constant velocity, usually by an acousto-optic modulator beam deflector, such that range measurements can be obtained very rapidly, at rates at least up to 20,000 range measurements per second. Nevertheless, even this high speed is insuffi­cient for some applications, including many that are motivating the development of 3-D cameras.
  • Fig. 3 shows the multiple channel optical flying spot triangulation ranger of this invention.
  • a signifi­cant increase in speed is achieved by adding additional detector channels, each of which observes the surface at a different point along the line which forms the intersection of the swept beam with the surface.
  • Four light detection channels are illustrated, but ten to twenty channels are feasible and a reasonable upper limit is thirty to forty channels. All of the detection channels make use of the same swept beam L, but there are now N range points per beam sweep, where N is the number of channels. Only the receiver channels must be duplicated to achieve the increased speed.
  • a laser (not shown) generates a narrow laser beam that is presented to acousto-optic beam deflector 16 and rapidly scanned across the surface 17 in the X direction.
  • a single spherical receiving lens 18 or a compound lens serves all of the light detection channels 19-1 to 19-4, the ends of which are encapsulated in a plastic plug 20.
  • the ends of the light transmitting channels extend out of the plug 20 and deliver light to four separate light detectors 21-1 to 21-4.
  • These may be photomultipliers, certain types of photodiodes, or other solid state light detectors. Photomultipliers are a good choice because they have ideal light detection qualities, i.e. excellent sensitivity and wide dynamic range.
  • an aperture stop plate 22 between the receiving lens 18 and the light detection channels, having a rectangular slit 23 to pass light.
  • This slit is relatively large, say 0.125" x 1.000", and functions to increase the depth of focus and limit passage of light, much like the f/stop on a camera.
  • This slit does not serve the same purpose as aperture 14 in the prior art single channel instrument, and is not an essential part of the system.
  • Light detection channel 19-1 receives light only from the sensitive zone 24-1 on surface 17, and the other three channels respectively from the sensitive zones 24-2, 24-3, and 24-4.
  • the shape of these sensitive zones is approximately the same as the entrance faces of the light detection channels and the size of the zones is governed by the magnification of the optical system.
  • a square or rec­tangular entrance face geometry is ideal; a small aperture is desired in the X direction and the longer Y dimension in the rectangular case gives freedom to align.
  • the detector head 20 is illustrated in perspective in Fig. 4.
  • Fig. 5 shows the use of fiber optic bundle technology to create the adjacent fiber optic channels 19-1 to 19-4.
  • Each channel is comprised of a noncoherent fiber optic bundle, rectangular at the entrance and gathered together toward the other end to make a flexible, roughly circular bundle that can be routed to the photo­multiplier box.
  • Fig. 6 shows solid glass light transmitting channels 26-1 to 26-4.
  • FST flying spot triangulation
  • Fig. 7 The scanning of a larger area on an object by coordinated X and Y scans, followed by indexing of a table on which the object rests to scan other strips on the object surface, is illustrated in Fig. 7.
  • the beam deflector 16 in Fig. 3 sweeps the laser beam L along a line in the X direction as was previously described. As the laser beam L enters and crosses the four sensitive zones 27, the respective light detection channels generate output signal pulses at times that are a function of range to the surface. Thus there are four image points per beam scan. Then a Y scan mirror 28 shown schematically in Fig.
  • strip 3 scans the beam in the Y direction and a second X scan beam scan is made to obtain four more range measurements. If strip 1 has 500 X beam sweeps and there are 4 range points per sweep, the total from strip 1 is 2000 range points. The table is now stepped in the X direction and strip 2 on the object surface is scanned, and so on.
  • Fig. 8 is a perspective drawing of the entire range camera and X-Y table arrangement to inspect a printed wiring board.
  • These boards consist of a thin planar sheet on which are mounted electronic components such as integrated circuits, resistors and capacitors. These components are interconnected by conductors on the board surface or by sets of conductors within the plane of the board.
  • the X-Y table 28 holds the printed circuit board 29 with the bottom, lead side facing down towards the optical head and parallel to the X-Y plane. The table scans the active measurement region over the entire surface of the printed circuit board.
  • the polygon mirrors assembly 30 rotates at a constant velocity and operates to Y scan the laser beam and as a Y descanner for the receiving optics.
  • the narrow beam generated by a laser 31 is deflected by the acousto-optic modulator 32 to perform the X scan.
  • the swept beam is reflected by folding mirrors onto the first polygon mirror 33 and hence sweeps across the surface of board 29.
  • the reflected beam is descanned by the second polygon mirror 34, focused by lens 50, and reflected by a mirror to the multichannel fiber optic bundles 35 which deliver light to the photomultiplier box 36.
  • the signal processing electronics block diagram in Fig. 9 illustrates parallel processing of the detector output signals and computation of range values.
  • the multichannel light detector assembly 37 has three channels and, looking at one channel, the others being the same, the signal pulse from photomultiplier 38 is converted to a voltage and conditioned in amplifier 39 and digitized at 40.
  • Digital signal processor 41 produces the best estimate of the time signal after rejecting any possible range clutter and noise impulses, accounts for variations in surface reflectivity and luminance, and calculates range or height of the surface.
  • the three computed range values are presented to buffer 42 and hence read out to the range computer 43. When all the range measurements are stored, a range image may be output.
  • the range computer coordinates the timing of the system and acousto-optic beam deflector 44, and may have other functions such as coordinate conversion.
  • the period T of one acousto-optic sweep is, for instance, 50-60 microseconds and is divided into time segments corres­ponding to beam angle.
  • the start of sweep (SOS) and end of sweep (EOS) are sent to digital processor 41 as well as the sample clock (SC).
  • SC sample clock
  • the detector signal pulse occurs at times t1, t2 and t3, respectively, measured from the start of sweep. These times are a function of range to the surface at those range points.
  • this time determines the angle of the swept beam and knowing the angle of the reflected beam, optical triangulation yields the range.
  • N range values are determined where N is the number of detection channels.
  • a practical upper limit to the total number of channels may be in the order of 30-40 channels.
  • One consideration is the complexity introduced by a large number of detectors and time analysis electronics.
  • Another limit is the required increase in scan length. This derives from the relationship between scan length and strip length.
  • the light beam L is shown scanned parallel and swept over the surface from time t0 time to t1.
  • the image of the multiple detection channels on the surface at the closest design range is shown at 48, and the image at farthest design range at 49.
  • S is much smaller than L, such that an insig­nificant change in sweep length is required to accommodate the additional channels. But as N is increased, the sweep length must be increased substantially, according to equation (1). This spreads out the light, weakening the signal to each channel.
  • fast scanners such as acousto-optic cells provide a limited number of resolution spots. If the scan is spread out too far, the scanned spot will have an instantaneous width greater than the resolved spot, further weakening the signal. Despite these limitations a very large improvement in data rate is realized within the scanned aperture configuration.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Length Measuring Devices By Optical Means (AREA)
  • Measurement Of Optical Distance (AREA)
  • Optical Radar Systems And Details Thereof (AREA)
EP19890302638 1988-03-18 1989-03-17 Système de triangulation Withdrawn EP0333493A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US169707 1988-03-18
US07/169,707 US4900146A (en) 1988-03-18 1988-03-18 Multiple channel optical flying spot triangulation ranger system

Publications (2)

Publication Number Publication Date
EP0333493A2 true EP0333493A2 (fr) 1989-09-20
EP0333493A3 EP0333493A3 (fr) 1991-07-03

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Family Applications (1)

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EP19890302638 Withdrawn EP0333493A3 (fr) 1988-03-18 1989-03-17 Système de triangulation

Country Status (4)

Country Link
US (1) US4900146A (fr)
EP (1) EP0333493A3 (fr)
JP (1) JPH01311206A (fr)
KR (1) KR970007040B1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0694771A1 (fr) * 1994-06-29 1996-01-31 BFI ENTSORGUNGSTECHNOLOGIE GmbH Dispositif de contrÔle optique

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US5088828A (en) * 1989-02-28 1992-02-18 Siemens Aktiengesellschaft Method and apparatus for three-dimensional testing of printed circuitboards
US5032023A (en) * 1990-07-02 1991-07-16 General Electric Company Optical fiber based sensor for a variable depth range camera
US5615003A (en) * 1994-11-29 1997-03-25 Hermary; Alexander T. Electromagnetic profile scanner
US5570183A (en) * 1995-04-24 1996-10-29 Ati Systems, Inc. Apparatus for measuring optical characteristics of a surface in two dimensions using a moving light source
US5822486A (en) * 1995-11-02 1998-10-13 General Scanning, Inc. Scanned remote imaging method and system and method of determining optimum design characteristics of a filter for use therein
US6705526B1 (en) 1995-12-18 2004-03-16 Metrologic Instruments, Inc. Automated method of and system for dimensioning objects transported through a work environment using contour tracing, vertice detection, corner point detection, and corner point reduction methods on two-dimensional range data maps captured by an amplitude modulated laser scanning beam
US20020014533A1 (en) 1995-12-18 2002-02-07 Xiaxun Zhu Automated object dimensioning system employing contour tracing, vertice detection, and forner point detection and reduction methods on 2-d range data maps
US5831621A (en) * 1996-10-21 1998-11-03 The Trustees Of The University Of Pennyslvania Positional space solution to the next best view problem
US5917600A (en) * 1997-06-18 1999-06-29 Cybo Robots, Inc Displacement sensor
US6118540A (en) * 1997-07-11 2000-09-12 Semiconductor Technologies & Instruments, Inc. Method and apparatus for inspecting a workpiece
US5956134A (en) * 1997-07-11 1999-09-21 Semiconductor Technologies & Instruments, Inc. Inspection system and method for leads of semiconductor devices
DE19961955A1 (de) * 1999-12-24 2001-07-05 Hannover Laser Zentrum Verfahren zur Messung eines Abstandes zwischen einer Meßvorrichtung und einer Meßoberfläche sowie Meßvorrichtung
US6870611B2 (en) 2001-07-26 2005-03-22 Orbotech Ltd. Electrical circuit conductor inspection
US6654115B2 (en) 2001-01-18 2003-11-25 Orbotech Ltd. System and method for multi-dimensional optical inspection
US7344082B2 (en) * 2002-01-02 2008-03-18 Metrologic Instruments, Inc. Automated method of and system for dimensioning objects over a conveyor belt structure by applying contouring tracing, vertice detection, corner point detection, and corner point reduction methods to two-dimensional range data maps of the space above the conveyor belt captured by an amplitude modulated laser scanning beam
DE102004003615B4 (de) * 2004-01-25 2005-12-15 Man Roland Druckmaschinen Ag Vorrichtung und Verfahren zur Erfassung und Auswertung eines Bildes von einem vorbestimmten Ausschnitt eines Druckerzeugnisses
KR100940259B1 (ko) * 2008-01-21 2010-02-04 (주)클래시스 다수의 레이저빔이 출력되는 의료용 레이저장치
DE102009040990A1 (de) * 2009-09-10 2011-03-17 Carl Zeiss Ag Vorrichtung und Verfahren zum Vermessen einer Oberfläche
US8812149B2 (en) 2011-02-24 2014-08-19 Mss, Inc. Sequential scanning of multiple wavelengths
US20140009762A1 (en) * 2012-06-21 2014-01-09 Nikon Corporation Measurement assembly with fiber optic array

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US4645917A (en) * 1985-05-31 1987-02-24 General Electric Company Swept aperture flying spot profiler
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Publication number Priority date Publication date Assignee Title
DE3044831A1 (de) * 1980-11-28 1982-06-24 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V., 8000 München Anordnung zur automatischen beruehrungslosen messung der raeumlichen lage von gegenstaenden
FR2539519A1 (fr) * 1983-01-18 1984-07-20 Asahi Optical Co Ltd Dispositif de mise au point automatique pour appareil photographique
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Cited By (3)

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Publication number Priority date Publication date Assignee Title
EP0694771A1 (fr) * 1994-06-29 1996-01-31 BFI ENTSORGUNGSTECHNOLOGIE GmbH Dispositif de contrÔle optique
US5668367A (en) * 1994-06-29 1997-09-16 Bfi Entsorgungstechnologie Gmbh Optical space monitoring apparatus comprising light guiding fibers transmitting light through the space to be monitored
USRE36094E (en) * 1994-06-29 1999-02-16 Bfi Entsorgungstechnologie Gmbh Optical space monitoring apparatus comprising light guiding fibers transmitting light through the space to be monitored

Also Published As

Publication number Publication date
KR970007040B1 (ko) 1997-05-02
KR890014994A (ko) 1989-10-28
EP0333493A3 (fr) 1991-07-03
JPH01311206A (ja) 1989-12-15
US4900146A (en) 1990-02-13

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